Fair Value Measurements (Fair Value Measurement Amounts for Assets and Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	$ 3,296
Derivative assets	282	$ 61
Total assets	10,723	9,748
Derivative liabilities	(423)	(324)
Net assets (liabilities)	10,300	9,424
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	4	1
Total assets	8,227	7,551
Net assets (liabilities)	8,227	7,551
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	253	53
Total assets	2,423	2,144
Derivative liabilities	(267)	(240)
Net assets (liabilities)	2,156	1,904
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	25	7
Total assets	25	7
Derivative liabilities	(156)	(84)
Net assets (liabilities)	(131)	(77)
Not Categorized
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	48	46
Net assets (liabilities)	48	46
NDTF
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	153	177
Equity securities, FV-NI	6,743	6,235
Debt securities, available-for-sale	3,012	2,717
NDTF | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	153	177
Debt securities, available-for-sale	1,066	874
NDTF | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,946	1,843
NDTF equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	6,743	6,235
NDTF equity securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	6,695	6,189
NDTF equity securities | Not Categorized
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	48	46
Other Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	83	127
Equity securities, FV-NI	166	146
Debt securities, available-for-sale	284	285
Other Investments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	83	127
Equity securities, FV-NI	166	146
Debt securities, available-for-sale	60	37
Other Investments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	224	248
Duke Energy Carolinas
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,468
Derivative assets	107	20
Total assets	5,553	4,985
Derivative liabilities	(7)	(20)
Net assets (liabilities)	5,546	4,965
Duke Energy Carolinas | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	4,338	3,861
Net assets (liabilities)	4,338	3,861
Duke Energy Carolinas | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	107	20
Total assets	1,167	1,078
Derivative liabilities	(7)	(20)
Net assets (liabilities)	1,160	1,058
Duke Energy Carolinas | Not Categorized
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	48	46
Net assets (liabilities)	48	46
Duke Energy Carolinas | NDTF
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	68	30
Equity securities, FV-NI	3,910	3,685
Debt securities, available-for-sale	1,468	1,250
Duke Energy Carolinas | NDTF | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	68	30
Debt securities, available-for-sale	408	192
Duke Energy Carolinas | NDTF | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,060	1,058
Duke Energy Carolinas | NDTF equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	3,910	3,685
Duke Energy Carolinas | NDTF equity securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	3,862	3,639
Duke Energy Carolinas | NDTF equity securities | Not Categorized
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	48	46
Progress Energy
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,571
Derivative assets	142	33
Total assets	4,635	4,329
Derivative liabilities	(17)	(29)
Net assets (liabilities)	4,618	4,300
Progress Energy | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	3,580	3,485
Net assets (liabilities)	3,580	3,485
Progress Energy | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	142	33
Total assets	1,055	844
Derivative liabilities	(17)	(29)
Net assets (liabilities)	1,038	815
Progress Energy | NDTF
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	85	147
Equity securities, FV-NI	2,833	2,550
Debt securities, available-for-sale	1,544	1,467
Progress Energy | NDTF | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	85	147
Debt securities, available-for-sale	658	682
Progress Energy | NDTF | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	886	785
Progress Energy | NDTF equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,833	2,550
Progress Energy | NDTF equity securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,833	2,550
Progress Energy | Other Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	4	106
Debt securities, available-for-sale	27	26
Progress Energy | Other Investments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	4	106
Progress Energy | Other Investments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	27	26
Duke Energy Progress
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	1,061
Derivative assets	132	33
Total assets	3,997	3,562
Derivative liabilities	(4)	(14)
Net assets (liabilities)	3,993	3,548
Duke Energy Progress | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	3,073	2,773
Net assets (liabilities)	3,073	2,773
Duke Energy Progress | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	132	33
Total assets	924	789
Derivative liabilities	(4)	(14)
Net assets (liabilities)	920	775
Duke Energy Progress | NDTF
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	73	76
Equity securities, FV-NI	2,730	2,459
Debt securities, available-for-sale	1,061	993
Duke Energy Progress | NDTF | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	73	76
Debt securities, available-for-sale	269	237
Duke Energy Progress | NDTF | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	792	756
Duke Energy Progress | NDTF equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,730	2,459
Duke Energy Progress | NDTF equity securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	2,730	2,459
Duke Energy Progress | Other Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1	1
Duke Energy Progress | Other Investments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1	1
Duke Energy Florida
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	510
Derivative assets	10
Total assets	636	663
Derivative liabilities	(13)
Net assets (liabilities)	623	663
Duke Energy Florida | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	505	608
Net assets (liabilities)	505	608
Duke Energy Florida | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	10
Total assets	131	55
Derivative liabilities	(13)
Net assets (liabilities)	118	55
Duke Energy Florida | NDTF
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	12	71
Equity securities, FV-NI	103	91
Debt securities, available-for-sale	483	474
Duke Energy Florida | NDTF | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	12	71
Debt securities, available-for-sale	389	445
Duke Energy Florida | NDTF | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	94	29
Duke Energy Florida | NDTF equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	103	91
Duke Energy Florida | NDTF equity securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, FV-NI	103	91
Duke Energy Florida | Other Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1	1
Debt securities, available-for-sale	27	26
Duke Energy Florida | Other Investments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1	1
Duke Energy Florida | Other Investments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	27	26
Duke Energy Indiana
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	45
Derivative assets	24	6
Total assets	180	149
Derivative liabilities		(1)
Net assets (liabilities)	180	148
Duke Energy Indiana | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2
Total assets	113	98
Derivative liabilities		(1)
Net assets (liabilities)	113	97
Duke Energy Indiana | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	45	45
Net assets (liabilities)	45	45
Duke Energy Indiana | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	22	6
Total assets	22	6
Net assets (liabilities)	22	6
Duke Energy Indiana | Other Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1	1
Equity securities, FV-NI	110	97
Debt securities, available-for-sale	45	45
Duke Energy Indiana | Other Investments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1	1
Equity securities, FV-NI	110	97
Duke Energy Indiana | Other Investments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, available-for-sale	45	45
Piedmont
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	1
Derivative liabilities	(161)	(122)
Net assets (liabilities)	(159)	(121)
Piedmont | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	1
Net assets (liabilities)	2	1
Piedmont | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	(161)	(122)
Net assets (liabilities)	$ (161)	$ (122)